![]() ![]() Because the air mass loses the heavy isotopes ( 2H and 18O) faster than the light isotopes, the heavy isotope is distilled from the air mass. ![]() The most fundamental example of this process involves the progressive drying of an air mass that has become saturated with water over the oceans and then travels over land. This partitioning among the phases is at the root of most applications involving water isotopes, because it leads to progressive evolution of the water isotope composition of climatological air masses as they move across the surface of the earth gaining and losing moisture. Of these, 1H, 2H, 16O and 18O are abundant and can be easily measured by mass spectrometry.Ī simple rule governs the partitioning of water isotopes in most hydrological processes: heavy isotopes occur preferentially in liquid (or solid) phases and the light isotopes in the gaseous phase. Two stable isotopes of hydrogen ( 1H and 2H) and three of oxygen ( 16O, 17O and 18O) occur naturally in waters and in biological and geological materials. All rights reserved.The stable isotopes of hydrogen and oxygen have a long history of use in hydrology and paleoclimatology. Light absorption Molecular compositions Wood pyrolysis and combustion.Ĭopyright © 2021 Elsevier B.V. These results indicated that molecules with larger MW and a high level of unsaturation and aromaticity present higher light absorption, while molecules with high elemental ratios of H/C, O/C, N/C, and S/C are adverse to light absorption. The molecular weight (MW), double bonds equivalent (DBE), DBE/C, and modified aromaticity index (AI mod) of extracted OC showed higher values in MSOC than those in WSOC, and higher values under the N 2 atmosphere than those under the air atmosphere. ![]() Although the FTIR spectra showed identical functional groups for the OC from the air and N 2 conditions, molecular compositions from the FT-ICR MS analysis presented significant differences. These results indicated that OC extracted by methanol has higher light absorption, especially for the OC emitted from the N 2 pyrolysis atmosphere. Moreover, the MAE 365 values derived from the N 2 pyrolysis atmosphere are higher than that from the air atmosphere for both MSOC and WSOC. The light absorption properties showed that the mass absorption efficiency at 365 nm (MAE 365) of methanol-soluble OC (MSOC) is 3.1-3.8 times higher than that of water-soluble OC (WSOC). The absorption spectra, chemical functional groups, and molecular compositions of OC were analyzed using UV-Vis-NIR spectrophotometer, Fourier transform infrared spectroscopy (FTIR), and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), respectively. In this work, primary OC emitted from wood pyrolysis and combustion under nitrogen (N 2) and air conditions in a tube furnace was investigated. Organic carbon (OC) emitted from biomass burning (BB) plays an important role in the global radiation budget.
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